The present invention relates to a fuel injector.
More specifically, the present invention relates to a fuel injector for an internal combustion engine, to which the following description refers purely by way of example.
A known internal combustion engine fuel injector comprises a tubular injector body extending along a given axis; and a valve housed in a seat in the injector body and comprising a tubular valve body fixed inside the injector body seat and coaxial with the injector body. The injector has an annular chamber defined by the injector body and the valve body, which have respective annular shoulders separated by a given distance equal to the height of the annular chamber.
To form the injector, the valve body is fixed to the injector body in a given position along the axis by means of further shoulders formed on the valve and injector bodies and resting against each other, and by means of a ring nut which engages a threaded portion of the injector body and pushes the valve body axially against the injector body to keep the further shoulders in contact with each other. The injector also comprises a seal housed inside the annular chamber to prevent the high-pressure fuel fed into the annular chamber from leaking between the injector body and the valve body.
The method of producing the above injector comprises forming shoulders on the injector body and valve body to form the annular chamber; threading a portion of the injector body; forming further shoulders on the valve body and injector body to define a given axial position of the valve body with respect to the injector body; and assembling a seal and ring nut.
It is an object of the present invention to provide a particularly fast method of producing an injector.
According to the present invention, there is provided a method of producing a fuel injector comprising a tubular injector body extending along a given axis; a tubular valve body housed inside a seat in the injector body and coaxial with the injector body; and an annular chamber defined by the injector body and the valve body; the method comprising connecting the valve body to the injector body, and fixing the valve body to the injector body in a given position along the axis; and the method being characterized in that the valve body is connected and fixed to the injector body by means of a driving operation to interference fit the valve body inside the seat in the injector body.
Interference fitting the valve body inside the seat in the injector body enables the valve body to be fixed in a given axial position with respect to the injector body without machining further shoulders or the thread, and with no need for a ring nut, and also ensures hermetic sealing between the valve body and the injector body, so that the seal inside the annular chamber, between the valve body and the injector body, for sealing the annular chamber can be dispensed with.
Eliminating machining and reducing the number of component parts of the injector enable the injector to be produced extremely quickly.
In one particular embodiment, the method comprises forming an annular groove on said valve body; said groove interrupting the outer cylindrical face of the valve body and defining said annular chamber together with the inner face of said seat.
The size of the annular chamber is defined solely by formation of the groove, and does not depend on the axial position of the valve body with respect to the injector body; and the forces generated by the fuel pressure are balanced along said given axis, unlike known injectors in which the axial forces are not balanced and any loosening of the ring nut alters the size of the annular chamber.
The present invention also relates to an injector.
According to the present invention, there is provided an injector comprising a tubular injector body extending along a given axis; a tubular valve body housed inside a seat in the injector body and coaxial with the injector body; and an annular chamber defined by the injector body and the valve body; the injector being characterized in that the valve body is fixed to the injector body by means of a driving operation to interference fit the valve body inside the seat in the injector body.